1. Field of the Invention
The present invention relates to an electronic apparatus, and more particularly, to an electronic apparatus that reduces power consumption.
2. Related Art
Electronic apparatuses, such as mobile personal computers (PCs) or other mobile devices, typically incorporate some form of power saving and power management techniques to reduce power consumption, particularly, from a battery in order to maximum available battery usage time.
One example of such power saving and power management techniques is to reduce signal voltages for signal transmission. However, as signal voltages have been lowered in electronic apparatuses, their respective circuits have suffered from signal reflections generated by impedance mismatches. Such reflections change signal waveforms, and cause overshoot or undershoot, thereby distorting signals. As a result, many electronic apparatuses employ a predetermined resistor (hereinafter, referred as a “terminating resistor”) in a signal transmission line to match the impedance of the respective circuits and prevent reflections. In addition, a memory of these electronic apparatuses is supplied with a predetermined voltage (hereinafter, referred as a “terminating voltage”). The terminating voltage together with the terminating resistor can raise the memory signal level and improve the memory processing speed.
FIG. 1 illustrates a typical memory and a memory controller usable in such an electronic apparatus.
As shown in FIG. 1, a memory 10 and a memory controller 20 are connected to each other through a transmission line 30 having a length corresponding to reflected signal waves. The transmission line 30 transmits a control signal, which is generated by the memory controller 20 according to a predetermined operating clock, to the memory 10.
A terminal of the transmission line 30 is connected to a terminating resistor 40 to match the impedance, and a terminating voltage 50 to raise the signal level.
Specifically, the control signal transmitted between the memory 10 and the memory controller 20 has a level between 0V and 1.8V, and raises the signal level as much as the terminating voltage 50. For example, if the terminating voltage 50 is 0.9V, the signal level of the control signal is changed to 0.9V-1.8V, from 0V-1.8V (i.e., the lowest value thereof is raised).
If the signal level rises as described in connection with FIG. 1, the voltage difference of the control signal is reduced, thereby making the timing of the control signal faster and improving the processing speed.
However, the terminating voltage 50 is only used to raise the signal level of the control signal. Accordingly, an electronic apparatus continuously consumes power due to the terminating voltage 50 even when such an electronic apparatus is in a standby mode, not performing any operation. As a result, electronic apparatuses such as notebook PCs, which employ a battery as a power source, consume more power, thereby decreasing usage time of the battery.
Thus, a new technique is required to reduce power consumption in such an electronic apparatus due to the terminating voltage 50.
Korean Patent First Publication No. 2002-0013388 discloses a directional combination type data transmission system which uses a traveling wave and a reflection wave generating total reflection by making a terminal of a main data transmission line between a DRAM memory and a memory controller an open terminal or a short terminal. Such an arrangement can narrow the intervals between DRAM memory banks, which allow individual memory banks to be installed more densely in the memory pack, and reduce the data writing latency time. However, Korean Patent First Publication No. 2002-0013388 does not disclose any method for reducing the increased power consumption caused by the voltage used for raising the signal level of the control signal.